1. Field of the Invention
The present invention relates to a steer-by-wire system and a control program therefor suitable for use in motor vehicles.
2. Discussion of the Related Art
Generally, in a steer-by-wire system for a motor vehicle, as described in Japanese unexampled, published patent application No. 2002-37112 for example, a steering handle and steerable road wheels are mechanically disconnected, and a steering actuator steers the steerable road wheels in dependence on the steering angle of the steering handle, while a reaction force generating actuator applies a steering reaction force to the steering handle. Further, there has been under development a steer-by-wire system which is capable of controlling a reaction force generating actuator to generate a steering reaction force in proportion to a drive electric current to a steering actuator.
By the way, in the steer-by-wire system under development, when the steerable road wheels are brought into state in which they are unable to steer anymore, the steering actuator comes to be overloaded, and therefore, the drive electric current to the steering actuator is restrained to avoid the overheating of the same.
However, in the steer-by-wire system under development, the steering reaction force is controlled to be decreased as the drive electric current to the steering actuator is limited or restrained, and it occurs therefore that the vehicle driver turns the steering handle excessively even in the state that the steerable road wheels are unable to steer further.